Musculoskeletal injuries and joint disorders due to sports, recreation and exercise (SRE) have reached epidemic proportions as our society attempts to develop a healthier lifestyle. Participation in many SRE activities requires maintenance of lower- extremity joint health, yet such involvement presents an inherent risk of developing exercise-induced or traumatic musculoskeletal injuries. Treatment of these injuries, particularly to the knee joint, is paramount in the retention of a healthy lifestyle. Studies of patients suffering knee injuries, such as to the anterior cruciate ligament (ACL) and meniscus, show that even with surgical reconstruction after traumatic rupture there is a significant increase in the risk of a long term, chronic disease called osteoarthritis (OA). We hypothesize that this disease process may be precipitated by occult damage to the other structures of the knee as a result of the high compressive joint loads that occur during the acute injury to the knee. High joint contact pressures during traumatic impaction help explain the large number of injury cases that exhibit bone bruises, or occult bone microcracks, and injury to overlying cartilage that occurs following injury- producing jump landings that often initiate the chronic disease process. Surprisingly, to date, there is no established animal model to study the long-term consequences of traumatic injury to the knee following rupture of the ACL and meniscal tissue. The current literature documents a joint instability model of osteoarthritis in which the ACL and/or meniscus is surgically damaged. However, this model fails to address the high contact pressures and tissue injuries generated in the joint during the acute event. This research team has recently developed a live animal model for the study of traumatic ACL and meniscus injury. In order to study the changes occurring in the tissues of the knee during traumatic injury and establish preliminary data for future clinical intervention studies, the current study will establish and characterize a new, in vivo animal model of traumatic joint injury. We hypothesize that there will be significantly more degeneration of the articular cartilage, remaining untorn menisci and subchondral bone during the degenerative phase of the traumatic versus the surgical model to 12 weeks post-trauma. The development of future orthopaedic treatments will hinge on accurate experimental models of post-injury inflammation, alignment, and pain issues. The proposed research has the potential to revolutionize the understanding of traumatic joint injury that leads to a post-traumatic OA by greatly altering the gold standard model used to study the pathology of knee OA. Future implementation of this characterized model will encourage translational treatments and interventions, such as rehabilitation therapies or pharmaceutical interventions, which will delay and potentially prevent joint pain, disability, and the eventual need for total knee arthroplasty.